Exploring PHP 8.5 pipe goodies

php85pipes.php

<?php

declare(strict_types=1);

// ISC License

// Copyright (c) 2025, Alexandre Gomes Gaigalas <alganet@gmail.com>

// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.

// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

function begin() {
    return (static fn () => yield from [])();
}

function check(Closure $fn, $message) : Closure {
    return static fn (Generator $it): Generator => yield from [
        ...$it,
        static fn ($v) => $fn($v) ? null : $message
    ];
}

function collect(Closure $step) : Closure {
    return static function (Generator $it) use ($step): Closure
    {
        $acc = static fn ($v) => [];
        foreach ($it as $fn) {
            $acc = static fn ($v) => $step($acc, $fn, $v);
        }
        return $acc;
    };
}

function allMustPass() : Closure {
    return collect(
        static fn ($acc, $fn, $v) => array_merge(
            $acc($v),
            (($m = $fn($v)) === null) ? [] : [$m]
        )
    );
}

function oneMustPass() : Closure {
    return collect(
        static fn ($acc, $fn, $v) => (($m = $fn($v)) === null)
            ? [] 
            : array_merge($acc($v), [$m])
    );
}

function validate(mixed $value): Closure {
    return static fn (Closure $fn) => $fn($value);
}

$base = fn () => begin()
    |> check(is_int(...), 'must be an integer')
    |> check(is_scalar(...), 'must be a scalar');

echo "Must be both int and scalar: 42 should return 0 messages\n";
var_dump($base() |> allMustPass() |> validate(42));

echo "Must be both int and scalar: 'hello' should return 1 message\n";
var_dump($base() |> allMustPass() |> validate('hello'));

echo "Must be either int or scalar: 42 should return 0 messages\n";
var_dump($base() |> oneMustPass() |> validate(42));

echo "Must be either int or scalar: [] should return 2 messages\n";
var_dump($base() |> oneMustPass() |> validate([]));